In The Republic, the main discussions are regarding the definition of justice and the motivation for appearing or being just. In Book I, Thrasymachus offers his definition of justice but it is dismissed through Socrates examination, Glaucon brings up Thrasymachus’ definition again in Book II only for it to be dismissed for the second time. But as the definition and value of justice is discussed more throughout The Republic, specifically Book IV, we see these questions being answered. Socrates discussion answers these questions of the defintion and the value of justice by showing justice is completely different than what Thrasymachus had described; justice is not actions taken but a organization that leads to virtue.
In Book I Thrasymachus defines justice as what's good for the stronger (338c). He uses his definition and his premises to prove this and that justice does not benefit those who are just, rather it benefits others. Justice allows for the strong to stay strong, while the weak stay weak. Since the stronger decide what is just, they benefit as they make the laws in their favor and those who are truly strong do not make mistakes as to what is in their advantage (340d). This shows that the unjust life reaps more benefits than the just life. Thrasymachus’ premises show the validity of his definition of justice, which is what is good for the stronger. His conclusion itself shows the divide in society: those who rule and those who are ruled. Whoever controls the city is its ruling power and the ruling power serves to make laws for the city’s good, and a ruling power exists in every nation. Thrasymachus says laws outline what is good for the ruler & just for the citizens, also those who break laws are punished for acting unjustly, therefore obeying the laws is just. He reasons that if every nation has a ruling power with laws that outline just behavior then it follows that every nation has the same ideals for justice; those ideals being that justice is what the stronger has decided to put into place (338e-339a5).
The are several reasons to criticise Thrasymachus’ argument, the biggest objection being the generalization of all ruling parties. The conclusion is built on two main assumptions: that every nation has a ruling power that is equal to the others and that every nation uses laws to define justice. First off, Thrasymachus lists only democracies, aristocracies, and tyrannies as the existing forms of government (338d7-8). To list these leads to the assumption that there exists no other form of government. I can infer that through proving his conclusion Thrasymachus assumes that all governments are equal to each other, but this idea is built on the assumption that a group will behave the same as an individual. A tyrant does not equal a king, a king does not equal a group of rulers; this is a false equivalency. All these ruling powers are not equal, so it is hard to believe that the way they rule and define just is equal. Secondly, every nation may not use laws as a way to define justice, the laws serve as guidelines of just actions and justice may be decided by the people through court or through a deity. Nations can lack laws and with the absence of laws, how would justice be defined? Could justice be defined? With the absence of a ruling party, how would justice be defined and would it exist? Thrasymachus’ entire argument relies upon the premise that justice is derived entirely from the actions and beliefs of a society’s ruling elite. This prevents it from having an identity when explored independently of the specific conditions that he laid out. Without these claims being true, his argument falls apart. Thrasymachus definition also now leads the question of the true value of justice which is answered through Socrates at the end of Book I and Book IV.
Socrates agrees with Thrasymachus’ idea that justice can be something that is good for another person, yet disagrees on the idea of it being for the stronger (339b/347). To prove that it is good to do what is good for the stronger, but at times to also do what is not, he goes through several premises as follows. Rulers are humans, therefore they are fallible and can enact laws which can be not in their own interest (or not good for the stronger). According to Thrasymachus, it is just for subjects to obey their rulers because this is justice. Therefore, there may be situations in which one should do the opposite of what the stronger says because they could be wrong? If the weaker were to obey poorly formulated laws, they could then be acting in the interest of themselves and not the interest of the stronger. Socrates argument fails to say when a citizen should listen to their ruler and when they should not, but if this is the case then no trust should be placed in rulers.If no trust is placed in rulers then it leads to a disorganized city, which is an unjust city by Socrates definition in Book IV. Also, if rulers make mistakes, then what is the motivation to follow anything they say when it could be wrong at any point? Socrates also fails to offer a different definition.
As the discussion delves deeper, a new question arises, is justice profitable? Is the just life preferable to the unjust life as Thrasymachus says? Socrates sets up premises to conclude that a just life is better than an unjust life. One being that the just man is associated with wisdom and goodness, conversely the unjust man is associated with ignorance and badness. Socrates says that in a city when injustice exists, different parts of the city are in disagreement with each other. Therefore, injustice in an individual means the different parts of him are in disagreement with each other and this may render him unable to act and less efficient. A just person's life is happier than an unjust person life because they have a good soul and this leads to a good life. These three ideas show how a just life is better than an unjust life, but still the definition of justice is still not present (350c-354).
Glaucon's brings Thrasymachus’ idea back in Book II and seeks that Socrates prove that justice belongs to the highest class of the three goods as Glaucon defines them. The three classes are goods we desire for itself and not for its results, things we value not for itself but for its results, things we value for itself and for its results (357a-358a3) Glaucon, aligns himself as neutral on justice and injustice, but decides to argue for injustice to allow Socrates to counter.
His three arguments against justice is that justice is a compromise, the practice of justice is done against one's will, and justice itself is not desirable the rewards of it are (558b-d11). Glaucon shows the nature of justice is that it's a compromise. People think that being wronged is worse than than the benefits of doing wrong, therefore they make agreements in the form of laws agreeing to not do wrong, so they can avoid being wronged themselves (358e-359b9). Glaucon’s second idea builds upon the first to claim that the practice of justice is done against one’s will. Justice is a compulsion, everyone thinks that injustice rears more material benefits than justice but act just due to the fear of societal judgment for their actions.. He recalls the tale of an ancestor of Gyges the Lydian who acquired a ring that allowed him to be invisible, when he realized the power of the ring he used it to act unjustly and eventually seized power of the state. This story shows any person will act unjustly if they know they will not be judged by these societal standards and be forced to comply due to fear of punishment; also it shows the true nature of men is to do wrong if they have the opportunity to, even a just man (359b10-361b8). Glaucon's last point is that justice itself is not desirable, only its rewards are. If a man is unjust but has a just appearance, then he will reap the benefits that are allowed to a just man. A just mans benefits are nearly endless due to his reputation: power in your city, ability to marry whoever you like, ability to marry your daughters to anyone you like, work with anyone he wants, he can be rich through unjust means, he will be successful in both the private and public sphere, and he can make better offerings to the gods to gain their favor. These examples show that it is better to be an unjust man with a just appearance rather than a truly just man because it allows for you to gain the benefits of being just without the typical compromises it entails (362b2-c11).
Glaucon’s three facets of justice work to support Thrasymachus’ earlier point that justice is what's good for the stronger. Justice is a compromise on what is best for the people, or in this case what is good for the stronger, and this is only reiterated by the second point which shows that if justice is compulsive then the stronger will only stay stronger through justice because people are compelled to follow the laws the stronger put in place. The third point proves this as well, justice being what's good for the stronger allows for the stronger to stay strong through reaping the benefits of appearing just and acting unjust.
In Book IV, justice is finally given a definition and its value is discussed by Socrates. Socrates’ definition of justice is the correct balance of the different parts of society in the best way that they benefit each other. As Socrates says, a just soul is a soul where the three parts: rational, spirited, and appetitive are balanced. A just soul correlates to a healthy soul so it is good to be just because it leads to health. Everyone desires health, so in order to achieve health everyone will act just. If every part of something is just, then it follows that the whole will be just, therefore if everyone in the city has a balanced, just soul then the city will be balanced and just as well (443c11-444a4). Injustice is the opposite, the three classes of society acting incorrectly, in a way where they are not balanced, and cause destruction to the city. (434c8-11). Socrates’ two different definitions of justice, based on the soul and based on the city show the value of justice. Within the person, it keeps the body and the soul healthy and balanced which allows for the person to live their best life. Within the city it allows for the city to run correctly and prosper. Because of the intrinsic value and external rewards of justice it has value, and this value is what makes it better than injustice, no matter what physical benefits being unjust can award you. This section of Book IV is very important because it answers the questions proposed in Book I and Book II: what is the definition is justice, what is the value of justice, and why is justice preferable to injustice.
In Book I and Book II, the definition and value of justice are discussed but these questions are left unanswered, until Socrates answers them in Book IV. Socrates’ definition and value of justice tie into Thrasymachus’ idea because of his integration of the city aspect. What is best for the city is the correct balance of all the parts, meaning they all must listen to a central power, and that central power is what’s stronger, they make the laws and the judgements. The central power makes the laws in their best interest and it is just for everyone below them to follow these laws.